The GLORIE Campaign: Assessment of the Capabilities of Airborne GNSS-R for Land Remote Sensing.

In June and July 2015 an intensive flight campaign was conducted over the south west of France to test the sensitivity of Global Navigation Satellite System Reflectometry (GNSS-R) to the geophysical parameters of continental surfaces. Namely, the parameters of interest were soil moisture, soil roughness, plant water content, forest biomass and level of inland water bodies and rivers. We used the GLORI polarimetric GNSS-R instrument, collecting raw 10MSPS 2-bit IQ direct (RHCP, zenith) and reflected (RHCP and LHCP, nadir) signals at GPS L1 frequency aboard the ATR-42 aircraft of the SAFIRE fleet. Simultaneous measurement of aircraft attitude and position were recorded. The flight plan included flyovers of several areas of interests, with collocated ground truth measurements of soil moisture, soil roughness, cultivated biomass, and forest biomass. Also flyovers of ponds, lakes and river were included for power calibration and altimetry retrievals. In total, 6 flights were performed between June 19th and July 6th, representing more than 15 hours of raw data. A conventional GNSS-R processing of the data was performed in order to compute the direct and reflected complex waveforms. A preliminary data analysis based on the variations of the ratio of reflected maximum correlation amplitude in the LHCP antenna to direct maximum correlated amplitude shows measurements sensitivity to soil type, land use and incidence angle. Also, first altimetric retrievals using phase-delay techniques shows very promising results over calm waters. Current work is ongoing in order to fit the observed polarimetric measurements with innovative bistatic scattering models capable of taking into account complex geometries and land use configurations.